yading@10: /*
yading@10:  * Delay Locked Loop based time filter
yading@10:  * Copyright (c) 2009 Samalyse
yading@10:  * Copyright (c) 2009 Michael Niedermayer
yading@10:  * Author: Olivier Guilyardi <olivier samalyse com>
yading@10:  *         Michael Niedermayer <michaelni gmx at>
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: #include "libavutil/common.h"
yading@10: #include "libavutil/mem.h"
yading@10: #include "config.h"
yading@10: #include "timefilter.h"
yading@10: 
yading@10: struct TimeFilter {
yading@10:     // Delay Locked Loop data. These variables refer to mathematical
yading@10:     // concepts described in: http://www.kokkinizita.net/papers/usingdll.pdf
yading@10:     double cycle_time;
yading@10:     double feedback2_factor;
yading@10:     double feedback3_factor;
yading@10:     double clock_period;
yading@10:     int count;
yading@10: };
yading@10: 
yading@10: /* 1 - exp(-x) using a 3-order power series */
yading@10: static double qexpneg(double x)
yading@10: {
yading@10:     return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3)));
yading@10: }
yading@10: 
yading@10: TimeFilter *ff_timefilter_new(double time_base,
yading@10:                               double period,
yading@10:                               double bandwidth)
yading@10: {
yading@10:     TimeFilter *self       = av_mallocz(sizeof(TimeFilter));
yading@10:     double o               = 2 * M_PI * bandwidth * period * time_base;
yading@10:     self->clock_period     = time_base;
yading@10:     self->feedback2_factor = qexpneg(M_SQRT2 * o);
yading@10:     self->feedback3_factor = qexpneg(o * o) / period;
yading@10:     return self;
yading@10: }
yading@10: 
yading@10: void ff_timefilter_destroy(TimeFilter *self)
yading@10: {
yading@10:     av_freep(&self);
yading@10: }
yading@10: 
yading@10: void ff_timefilter_reset(TimeFilter *self)
yading@10: {
yading@10:     self->count = 0;
yading@10: }
yading@10: 
yading@10: double ff_timefilter_update(TimeFilter *self, double system_time, double period)
yading@10: {
yading@10:     self->count++;
yading@10:     if (self->count == 1) {
yading@10:         self->cycle_time = system_time;
yading@10:     } else {
yading@10:         double loop_error;
yading@10:         self->cycle_time += self->clock_period * period;
yading@10:         loop_error = system_time - self->cycle_time;
yading@10: 
yading@10:         self->cycle_time   += FFMAX(self->feedback2_factor, 1.0 / self->count) * loop_error;
yading@10:         self->clock_period += self->feedback3_factor * loop_error;
yading@10:     }
yading@10:     return self->cycle_time;
yading@10: }
yading@10: 
yading@10: double ff_timefilter_eval(TimeFilter *self, double delta)
yading@10: {
yading@10:     return self->cycle_time + self->clock_period * delta;
yading@10: }
yading@10: 
yading@10: #ifdef TEST
yading@10: #include "libavutil/lfg.h"
yading@10: #define LFG_MAX ((1LL << 32) - 1)
yading@10: 
yading@10: int main(void)
yading@10: {
yading@10:     AVLFG prng;
yading@10:     double n0, n1;
yading@10: #define SAMPLES 1000
yading@10:     double ideal[SAMPLES];
yading@10:     double samples[SAMPLES];
yading@10:     double samplet[SAMPLES];
yading@10:     for (n0 = 0; n0 < 40; n0 = 2 * n0 + 1) {
yading@10:         for (n1 = 0; n1 < 10; n1 = 2 * n1 + 1) {
yading@10:             double best_error = 1000000000;
yading@10:             double bestpar0   = 1;
yading@10:             double bestpar1   = 1;
yading@10:             int better, i;
yading@10: 
yading@10:             av_lfg_init(&prng, 123);
yading@10:             for (i = 0; i < SAMPLES; i++) {
yading@10:                 samplet[i] = 10 + i + (av_lfg_get(&prng) < LFG_MAX/2 ? 0 : 0.999);
yading@10:                 ideal[i]   = samplet[i] + n1 * i / (1000);
yading@10:                 samples[i] = ideal[i] + n0 * (av_lfg_get(&prng) - LFG_MAX / 2) / (LFG_MAX * 10LL);
yading@10:                 if(i && samples[i]<samples[i-1])
yading@10:                     samples[i]=samples[i-1]+0.001;
yading@10:             }
yading@10: 
yading@10:             do {
yading@10:                 double par0, par1;
yading@10:                 better = 0;
yading@10:                 for (par0 = bestpar0 * 0.8; par0 <= bestpar0 * 1.21; par0 += bestpar0 * 0.05) {
yading@10:                     for (par1 = bestpar1 * 0.8; par1 <= bestpar1 * 1.21; par1 += bestpar1 * 0.05) {
yading@10:                         double error   = 0;
yading@10:                         TimeFilter *tf = ff_timefilter_new(1, par0, par1);
yading@10:                         for (i = 0; i < SAMPLES; i++) {
yading@10:                             double filtered;
yading@10:                             filtered = ff_timefilter_update(tf, samples[i], i ? (samplet[i] - samplet[i-1]) : 1);
yading@10:                             if(filtered < 0 || filtered > 1000000000)
yading@10:                                 printf("filter is unstable\n");
yading@10:                             error   += (filtered - ideal[i]) * (filtered - ideal[i]);
yading@10:                         }
yading@10:                         ff_timefilter_destroy(tf);
yading@10:                         if (error < best_error) {
yading@10:                             best_error = error;
yading@10:                             bestpar0   = par0;
yading@10:                             bestpar1   = par1;
yading@10:                             better     = 1;
yading@10:                         }
yading@10:                     }
yading@10:                 }
yading@10:             } while (better);
yading@10: #if 0
yading@10:             double lastfil = 9;
yading@10:             TimeFilter *tf = ff_timefilter_new(1, bestpar0, bestpar1);
yading@10:             for (i = 0; i < SAMPLES; i++) {
yading@10:                 double filtered;
yading@10:                 filtered = ff_timefilter_update(tf, samples[i], 1);
yading@10:                 printf("%f %f %f %f\n", i - samples[i] + 10, filtered - samples[i],
yading@10:                        samples[FFMAX(i, 1)] - samples[FFMAX(i - 1, 0)], filtered - lastfil);
yading@10:                 lastfil = filtered;
yading@10:             }
yading@10:             ff_timefilter_destroy(tf);
yading@10: #else
yading@10:             printf(" [%f %f %9f]", bestpar0, bestpar1, best_error);
yading@10: #endif
yading@10:         }
yading@10:         printf("\n");
yading@10:     }
yading@10:     return 0;
yading@10: }
yading@10: #endif